1. Field of the Invention
This invention relates to a photographic sensitive material, more particularly, to a photographic sensitive material having an antistatic layer containing not only a carboxylic acid polymer but also a carboxylic acid activating condensing agent that acts on the polymer to add appreciably to the physical strength of the antistatic layer.
2. Description of the Prior Art
Static buildup on photographic sensitive materials has long annoyed the photographic industry. Static electricity is generated during the manufacture and use of photosensitive materials when they are wound on rolls, rewound therefrom, transported on rollers or when they contact other objects in transit. Generation and accumulation of static charges is a product of, for example, the electric conductivity and triboelectric series of the photographic material, moisture, the properties of the contacted object as well as the atmosphere in which the contact occurs. Accumulated static electricity sometimes discharges to cause irregular fogging of the photosensitive material. This is so deleterious to the material that it may even lose its commercial value. For instance, an X-ray film, even if it experiences the slightest fogging, not only fails to achieve the intended purpose but may result in an inaccurate diagnosis.
It is well known to provide an antistatic layer in a photographic material so as to avoid any adverse effect of static buildup and many types of photographic materials have been proposed that incorporate an antistatic layer that dissipates static charges. Illustrative examples include U.S. Pat. Nos. 2,649,374, 3,033,679, 3,437,487, 3,525,621, 3,630,740, and 3,681,070. These references describe various antistats and antistatic layers that contain them. However, all these conventional antistatic agents or antistatic layers have serious defects that make them unsuitable for use as a component of a photographic sensitive material. For example, due to their poor function, they are unable to prevent fogging from occurring in a high-sensitivity photographic material, or the antistatic layer may dissolve in a developing bath to form scum, or the layer or the photographic material that contains it is so low in strength that it becomes less abrasion-resistant or durable until it is no longer of value as a commercial product or may cause troubles in the production line.
British Pat. No. 1,496,027 proposes an improved antistatic layer free from these defects which comprises (a) a water-soluble, film-forming anionic high molecular electrolyte in the form of a free acid (e.g., polystyrenesulfonic acid), (b) a film-forming, water-soluble, crosslinkable high molecular binder (e.g., polyvinyl alcohol) and (c) a cross-linking agent for said high molecular binder (e.g., glyoxal). However, the antistatic layer of this patent is such that it fixes the water-soluble, electrically conductive, anionic high molecular electrolyte within the network structure formed by the binder and the cross-linking agent therefor, and as a result, it cannot prevent dissolution of the electrolyte in a developing bath which unavoidably leads to a low pH and scum formation. In addition, the anionic electrolyte accounts for about a third to half the weight of the antistatic layer. In other words, a third to half of the antistatic film is not crosslinked and this insufficiency in the physical strength of the film poses a serious problem in the high-speed production of photographic light-sensitive materials.